IP-based mobile systems provide for communication between at least one mobile node and a wireless communication network. The term “mobile node” includes a mobile communication unit (e.g., mobile terminal, “smart phones,” nomadic devices such as laptop PCs with wireless connectivity, as described in greater detail below). Among other elements, the wireless communication system includes a home network and a foreign network. The mobile node may change its point of attachment to the Internet through these networks, but the mobile node will always be associated with a single home network for IP addressing purposes. The home network includes a home agent and the foreign network includes a foreign agent—both of which control the routing of information packets into and out of their network.
The mobile node, home agent and foreign agent may be called different names depending on the nomenclature used on any particular network configuration or communication system. For instance, a “mobile node” encompasses PC's having cabled (e.g., telephone line (“twisted pair”), Ethernet cable, optical cable, and so on) connectivity to the wireless network, as well as wireless connectivity directly to the cellular network, as can be experienced by various makes and models of mobile terminals (“cell phones”) having various features and functionality, such as Internet access, e-mail, messaging services, and the like. Mobile nodes are sometimes called a user equipment, mobile unit, mobile terminal, mobile device, or similar names depending on the nomenclature adopted by particular system providers. Generally, there is also a correspondence node, which may be mobile or fixed, that may be located on the network for communicating with the mobile node.
A home agent may also be referred to as a Local Mobility Anchor, Home Mobility Manager, Home Location Register, and a foreign agent may be referred to as a Mobile Access Gateway, Serving Mobility Manager, Visited Location Register, and Visiting Serving Entity. The terms mobile node, home agent and foreign agent are not meant to be restrictively defined, but could include other mobile communication units or supervisory routing devices located on the home or foreign networks. Foreign networks can also be called serving networks.
Registering the Mobile Node
Foreign agents and home agents periodically broadcast an agent advertisement to all nodes on the local network associated with that agent. An agent advertisement is a message from the agent on a network that may be issued under the Mobile IP protocol (RFC 2002) or any other type of communications protocol. This advertisement should include information that is required to uniquely identify a mobility agent (e.g. a home agent, a foreign agent, etc.) to a mobile node. Mobile nodes examine the agent advertisement and determine whether they are connected to the home network or a foreign network.
The mobile node will always be associated with its home network and sub-network for IP addressing purposes and will have information routed to it by routers located on the home and foreign network. If the mobile node is located on its home network, information packets will be routed to the mobile node according to the standard addressing and routing scheme. If the mobile node is visiting a foreign network, however, the mobile node obtains appropriate information from the agent advertisement, and transmits a registration request message (sometimes called a binding update request) to its home agent through the foreign agent. The registration request message will include a care-of address for the mobile node. A registration reply message (also called a binding update acknowledge message) may be sent to the mobile node by the home agent to confirm that the registration process has been successfully completed.
The mobile node keeps the home agent informed as to its location on foreign networks by registering a “care-of address” with the home agent. The registered care-of address identifies the foreign network where the mobile node is located, and the home agent uses this registered care-of address to forward information packets to the foreign network for subsequent transfer onto the mobile node. If the home agent receives an information packet addressed to the mobile node while the mobile node is located on a foreign network, the home agent will transmit the information packet to the mobile node's current location on the foreign network using the applicable care-of address. That is, this information packet containing the care-of address will then be forwarded and routed to the mobile node on the foreign network by a router on the foreign network according to the care-of address.
Multiple interfaces may be supported on a single or multiple foreign networks, which can include the different communication access types 802.11d, 802.11g, HRPD, WiFi, WiMax, CDMA, or LTE apart from the circuit-switched type of telephone communication access types. Problems can be encountered when the mobile node becomes coupled to different access types on a single or multiple networks, or when hand-over procedures are performed from one access type to another access type. When mobile nodes move from one foreign network to another foreign network, problems are sometimes encountered with the registration of the care of addressing with the home agent or local mobility anchor. For instance, problems can arise with hand-off procedure for a communication when the home agent or local mobility anchor may drop packets or bill for dropped packets, which can disrupt transmissions and cause billing discrepancies. (e.g. billing the subscriber for packets that were never received).